Ultra high strength alloy for severe oil and gas environments and method of preparation

Abstract

A high strength, corrosion resistant alloy suitable for use in oil and gas environments includes, in weight percent: 0-15% Fe, 18-24% Cr, 3-9% Mo, 0.05-3.0% Cu, 4.0-6.5% Nb, 0.5-2.2% Ti, 0.05-1.0% Al, 0.005-0.040% C, balance Ni plus incidental impurities and deoxidizers. A ratio of Nb/(Ti+Al) is equal to 2.5-7.5.

The invention claimed is: 
     
       1. A high strength, corrosion resistant alloy suitable for use in oil and gas environments, consisting of, in weight %: greater than zero and up to 15% Fe, 18-24% Cr, 5.4 to less than 7% Mo, 0.05-3.0% Cu, 4.0-6.5% Nb, 1.1-2.2% Ti, 0.05-0.7% Al, 0.005-0.040% C, balance Ni plus incidental impurities and deoxidizers, wherein a ratio of Nb/(Ti+Al)=2.5−7.5, wherein the alloy is in an annealed and age hardened condition, and wherein the alloy has a minimum yield strength of 120 ksi. 
     
     
       2. The alloy of  claim 1 , wherein the maximum Fe content is 12%. 
     
     
       3. The alloy of  claim 1 , wherein the minimum Cu content is 0.1%. 
     
     
       4. The alloy of  claim 1 , wherein the minimum Cu content is 1.0%. 
     
     
       5. The alloy of  claim 1 , wherein the minimum Ti content is 0.8%. 
     
     
       6. The alloy of  claim 1 , wherein the C content is less than 0.030%. 
     
     
       7. A bar or tube suitable for use in oil and gas wells made of the alloy of  claim 1 . 
     
     
       8. The alloy of  claim 1 , wherein the minimum Fe content is 5%. 
     
     
       9. The alloy of  claim 1 , wherein the minimum Cr content is 19%. 
     
     
       10. The alloy of  claim 1 , wherein the maximum Cr content is 23%. 
     
     
       11. The alloy of  claim 1 , wherein the maximum Cr content is 22%. 
     
     
       12. The alloy of  claim 1 , wherein the minimum Nb content is 4.2%. 
     
     
       13. The alloy of  claim 1 , wherein the maximum Nb content is 6.4%. 
     
     
       14. The alloy of  claim 1 , wherein the maximum Nb content is 6.3%. 
     
     
       15. The alloy of  claim 1 , wherein the maximum Nb content is 6.2%. 
     
     
       16. The alloy of  claim 1 , wherein the maximum Ti content is 2.0%. 
     
     
       17. The alloy of  claim 1 , wherein the maximum Ti content is 1.5%. 
     
     
       18. The alloy of  claim 1 , wherein the minimum Al content is 0.1%. 
     
     
       19. The alloy of  claim 1 , wherein the maximum Al content is 0.5%. 
     
     
       20. The alloy of  claim 1 , wherein the minimum Ni content is 35%. 
     
     
       21. The alloy of  claim 1 , wherein the minimum Ni content is 40%. 
     
     
       22. The alloy of  claim 1 , wherein the minimum Ni content is 50%. 
     
     
       23. The alloy of  claim 1 , wherein the maximum Ni content is 70%. 
     
     
       24. The alloy of  claim 1 , wherein the maximum Ni content is 60%. 
     
     
       25. The alloy of  claim 1 , wherein the C content is less than 0.020%. 
     
     
       26. The alloy of  claim 1 , wherein the maximum Mo content is 6.2%. 
     
     
       27. The alloy of  claim 1 , wherein the alloy has at least one of:
 a slow strain rate corrosion time-to-failure (TTF) environment to air ratio of at least 1.03 for up to 25 hours of exposure, and 
 a slow strain rate corrosion percent elongation (%EL) environment to air ratio of at least 1.04 for up to 25 hours of exposure, 
 wherein the slow strain rate corrosion TTF environment is 347° F. in a 20 wt. % NaCI solution under 500 psig CO 2  and 500 psig.